Electrochemical Splitting of LiF: A New Approach to Lithium-Ion Battery Materials

Dimov, Nikolay; Kitajou, Ayuko; Hori, Hironobu; Kobayashi, Eiji; Okada, Shigeto

doi:10.1149/05812.0087ecst

Cited by 22 publications

(33 citation statements)

References 16 publications

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“…The characteristic profile of LiF-MnO is displayed in a full cell with Li 4 Ti 5 O 12 negative electrode ( Supplementary Fig. 5) 14 . LiF-FeO and LiF-CoO nanocomposites delivered discharge capacities of 310 and 206 mAh g −1 , respectively, demonstrating the general applicability of metal oxides used as positive electrodes when mixed with LiF (Fig.…”

Section: Lif-mo Nanocomposite As Positive Electrodementioning

confidence: 99%

Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

et al. 2017

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Lithium-ion batteries based on intercalation compounds have dominated the advanced portable energy storage market. The positive electrode materials in these batteries belong to a material group of lithium-conducting crystals that contain redoxactive transition metal and lithium. Materials without lithium-conducting paths or lithium-free compounds could be rarely used as positive electrodes due to the incapability of reversible lithium intercalation or the necessity of using metallic lithium as negative electrodes. These constraints have significantly limited the choice of materials and retarded the development of new positive electrodes in lithium-ion batteries. Here, we demonstrate that lithium-free transition metal monoxides that do not contain lithium-conducting paths in their crystal structure can be converted into high-capacity positive electrodes in the electrochemical cell by initially decorating the monoxide surface with nanosized lithium fluoride. This unusual electrochemical behaviour is attributed to a surface conversion reaction mechanism in contrast with the classic lithium intercalation reaction. Our findings will o er a potential new path in the design of positive electrode materials in lithium-ion batteries.

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Section: Lif-mo Nanocomposite As Positive Electrodementioning

confidence: 99%

Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

et al. 2017

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“…Whatever the reaction mechanism, these composites were shown to gain their electrochemical activity by oxidation above 4.5 V, a voltage range at which LiPF 6 -based electrolytes are known to slightly decompose. [18,19] When cycled under the same condition, the cell with LiF-free MnO as positive electrode shows an initial discharge capacity of 14 mA h g −1 which progressively increases to 156 mA h g −1 at the 60th cycle prior to stabilization, while maintaining a coulombic efficiency of 94%. With this in mind we re-examined the electrochemical activity of MnO-LiF composite with a special attention dedicated to the role of LiF by using either ball-milled MnO-LiF composites or only MnO as positive electrode.…”

mentioning

confidence: 98%

“…Their electrochemical performance was tested in Swageloktype cells using a commercial LiPF 6 electrolyte (LP30), and the results are shown in Figure 1. [18,19] When cycled under the same condition, the cell with LiF-free MnO as positive electrode shows an initial discharge capacity of 14 mA h g −1 which progressively increases to 156 mA h g −1 at the 60th cycle prior to stabilization, while maintaining a coulombic efficiency of 94%. For the cell using the MnO-LiF composite as the positive electrode, there is the appearance of a long plateau at high voltage (≈4.6V) on oxidation followed by a smooth voltage decay to 1.5 V on discharge.…”

mentioning

confidence: 98%

“…Their electrochemical performance was tested in Swageloktype cells using a commercial LiPF 6 electrolyte (LP30), and the results are shown in Figure 1. [13][14][15][16][17] This approach was followed by Kang [18] and Okada and co-workers [19] using binary metal oxide and LiF to prepare cathode redox composites according to the following reaction [MO + LiF ↔ MOF + Li + + e − ], where the transition metal acts as electron reservoir and LiF provides Li + . For the cell using the MnO-LiF composite as the positive electrode, there is the appearance of a long plateau at high voltage (≈4.6V) on oxidation followed by a smooth voltage decay to 1.5 V on discharge.…”

mentioning

confidence: 99%

“…Note that the first charge is significantly different from the second one, in agreement with previous results with the first plateau being ascribed to the electrochemical activation of MnO via the decomposition of LiF to lead to an active "Mn-O-F" phase. [13][14][15][16][17] This approach was followed by Kang [18] and Okada and co-workers [19] using binary metal oxide and LiF to prepare cathode redox composites according to the following reaction [MO + LiF ↔ MOF + Li + + e − ], where the transition metal acts as electron reservoir and LiF provides Li + . Interestingly, for both cells (See Figure 1c) the derivative curves superimpose, indicating that once the formation step is achieved, both cells possess the same electrochemically active phase, most likely "Mn-O-F" type species.…”

mentioning

confidence: 99%

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Triggering the In Situ Electrochemical Formation of High Capacity Cathode Material from MnO

Zhang

Chen

Berg

et al. 2016

Advanced Energy Materials

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exact mechanism by which such reactions occur are not fully understood, since MnOF phases have never been reported so far. Whatever the reaction mechanism, these composites were shown to gain their electrochemical activity by oxidation above 4.5 V, a voltage range at which LiPF 6 -based electrolytes are known to slightly decompose. Thus, an open question deals with whether such electrolyte decomposition could serve as a source of F − . With this in mind we re-examined the electrochemical activity of MnO-LiF composite with a special attention dedicated to the role of LiF by using either ball-milled MnO-LiF composites or only MnO as positive electrode. We show here the feasibility to achieve discharge capacity over 300 mA h g −1 , a value much comparable to Li-rich layered oxides, for MnO electrodes at room temperature by simply relying on the use of fluorine from LiPF 6 decomposition.As a proof of concept, two sets of composite, one with MnO and LiF (in 50 mol% excess) and the other with only MnO, were, respectively, mixed with 20 wt% of carbon SuperP for 2 h. The resulting electrode powders consist of inhomogeneous particles having size ranging from 50 nm to 1-2 µm as confirmed using a JEOL JEM 6700F field-emission scanning electron microscope as shown in Figure S1 (Supporting Information). Their electrochemical performance was tested in Swageloktype cells using a commercial LiPF 6 electrolyte (LP30), and the results are shown in Figure 1. It is worth mentioning that all the electrochemical results reported herein have at least been reproduced twice. For the cell using the MnO-LiF composite as the positive electrode, there is the appearance of a long plateau at high voltage (≈4.6V) on oxidation followed by a smooth voltage decay to 1.5 V on discharge. Afterward, the cell shows a sustained reversible capacity of 115 mA h g −1 using a current density of 5 mA g −1 . Note that the first charge is significantly different from the second one, in agreement with previous results with the first plateau being ascribed to the electrochemical activation of MnO via the decomposition of LiF to lead to an active "Mn-O-F" phase. [18,19] When cycled under the same condition, the cell with LiF-free MnO as positive electrode shows an initial discharge capacity of 14 mA h g −1 which progressively increases to 156 mA h g −1 at the 60th cycle prior to stabilization, while maintaining a coulombic efficiency of 94%. Interestingly, for both cells (See Figure 1c) the derivative curves superimpose, indicating that once the formation step is achieved, both cells possess the same electrochemically active phase, most likely "Mn-O-F" type species. This implies that the LiPF 6 salt, aside from serving as Li + carrier, also provides F − species through the oxidation process. Thus, we demonstrate that the in situ preparation of F-based MnO composites is nested in the availability of F − coming from LiF, LiPF 6 , or both. At this stage a question arises with regards to the efficacy of the process depending upon how we introduce Continuous efforts ...

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Low‐Overpotential LiF Splitting in Lithiated Fluoride Conversion Cathode Catalyzed by Spinel Oxide

Wei

Zhao

Chen

et al. 2021

Adv Funct Materials

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Conversion chemistry involving LiF splitting is an appealing route toward high capacity cathodes for Li‐ion batteries. In general, cathodes based on LiF splitting need a redox host to provide the driving force for LiF decomposition from the surface. However, most of the systems are still far from practical owing to their limitations, especially the high charge voltage (4.5–5.0 V) needed to fully utilize the capacity and the subsequent low energy efficiency (<80%). The redox host is apparently the key to further reduce the required charge voltage and improve the energy efficiency. Here, a new LiF–NiFe2O4 conversion cathode chemistry is designed and demonstrated with a crystalline spinel oxide redox host. It is demonstrated that the new host effectively improves the surface redox and LiF splitting kinetics, which enable the new cathode to work at much lower charge cutoff voltage (4.2 V) without compromising the delivered capacity and voltage. The LiF–NiFe2O4 composite thin film is able to be discharged with large capacity of 237 mA h g−1 with high energy efficiency (88%), substantial pseudocapacitance contribution (>90%), and satisfactory capacity retention. This result indicates LiF splitting chemistry can become practical by carefully tailoring the redox host chemistry and optimizing the composition.

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Electrochemical Splitting of LiF: A New Approach to Lithium-Ion Battery Materials

Cited by 22 publications

References 16 publications

Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

Triggering the In Situ Electrochemical Formation of High Capacity Cathode Material from MnO

Low‐Overpotential LiF Splitting in Lithiated Fluoride Conversion Cathode Catalyzed by Spinel Oxide

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